total number of consumers in each region (CONSUM_mt)
total number of consumers of seven firms in each region (F1_mt, F2_mt,
F3_mt, F4_mt, F5_mt, F6_mt, F7_mt)

I want to calculate the four firm concentration ratio for each region,
C4_mt, which is the proportion of the number of consumers of top four
firms to the total number of consumers in that region, in percentage